Onion weed

Onion weed

Botanical Name: Allium triquetum

Family: Liliaceae (lily)

Also known as: Three-cornered garlic

Where is it originally from?: Mediterranean

What does it look like?

Grass-like perennial (<60 cm) with a strong garlic smell, growing from main bulbs (<10-15 mm diameter) and producing offset bulbs. Fleshy, straight leaves (2-5, each 20-60 cm long), with white papery sheaths, usually die back in late Spring. Fleshy, soft, 3-sided flower stalk (20-60 cm high) is surrounded by leaves at the base, and supports bell-shaped flowers (10-15 mm long, Oct-Nov) that are 5-petalled and are white with green stripes on each petal. Seed capsules (7 mm diameter) contain black seeds.

Are there any similar species?

Wild onion (A. vineale) has rush-like stems. Snowflake (Leucojum aestivum) and Nothoscordum inodorum lack garlic odour.

Why is it weedy?

Seeds and offset bulbs ensure distribution. Tolerates hot and cold, wind, semi-shade, damp heavy soils. Intolerant of strong competition for space, heavy shade.

How does it spread?

Seed and bulbs are spread via water and soil movement, dumped vegetation, contaminated machinery and nursery plants. Sources include wasteland, roadsides, sprayed areas, hedgerows, gardens.

What damage does it do?

Forms dense mats in Winter/Spring in disturbed sites, discourages native species from establishing.

Which habitats is it likely to invade?

Disturbed forest and shrubland, streamsides, herbfield, bare land, especially after spraying or other clearance to bare land.

What can I do to get rid of it?

1. Dig out small patches (all year round): dispose of at refuse transfer station, burn or bury.
2. Overall spray: metsulfuron-methyl 600g/kg (3g/10L).

What can I do to stop it coming back?

Spraying with glyphosate only gives plant more room to expand. Better to overplant with taller spp. In regenerating habitats, often better to leave altogether to minimise disturbance.